People come in all shapes and sizes, and this can occasionally create difficulty in shared seating situations, such as on busses, trains and airplanes. With increased usage of ride-sharing concepts, such as shared, hailed vehicles, this can create potential new problems in a much more cramped space, as most vehicle interiors are far less spacious than mass-transportation options. Also, seats are not always as clearly delineated as they are on planes, for example, and so two or three people attempting to share a ride, who may all require significant space, may find themselves in an uncomfortable or even impossible situation. This can lead to awkwardness and lost fares for a driver, and generally may discourage certain people from even attempting to use any service other than hailed, unshared rides. Even in those situations, if a six foot ten inch person hails a vehicle, and the driver is driving a two door compact, uncomfortableness and/or impossibility may result.
Most vehicle seats can be adjusted in some manner, and in the future autonomous vehicles may include much more dynamically reconfigurable seating. But even if a seat can be adjusted, there is currently little to no accommodation to address the potential pitfalls of tall or otherwise large occupants attempting to share an already partially-occupied ride.